This invention relates generally to conveyor belt weighing systems, and more particularly to a system, and a method for calibrating this system, for accurately weighing material transported by the system despite variations in the angle of inclination of the conveyor to the horizontal.
The weighing of material in many industrial situations, such as coal and iron mines, is accomplished by the continuous weighing method. This method uses weigh scales of the type with which the present invention is concerned in conjunction with belt conveyors that transport the bulk materials. The amount of conveyed material can be determined by continuously weighing the material passing over the weigh scale in a known period of time. In general, the continuous weighing method is extremely accurate as long as the belt scale is operated in a horizontal plane.
The difficulty has been that the weigh bridge is generally calibrated for a horizontal conveyor, and this calibration is not adjusted when the conveyor angle is changed either upwardly or downwardly. If the calibration is adjusted for a change in the conveyor angle, it is generally modified as a function of the cosine of the conveyor angle. Accordingly, for a positive (upward) conveyor angle, the modification factor used as 1/cos. Further, no modification factor is suggested for a negative (downward) conveyor angle.
Thus, there exists a need for a method of calibrating a belt scale wherein a calibration factor is defined to adjust the output signal of weigh bridge when the conveyor is inclined at either a negative or positive angle.